A turbofan type gas turbine engine includes a gas turbine core having a low pressure compressor, high pressure compressor, combustor, a high pressure turbine and a low pressure turbine in serial flow relationship. The gas turbine is operable in a known manner to generate a primary gas flow. The high pressure turbine and the low pressure turbine generally include annular arrays (“rows”) of stationary vanes or nozzles that direct combustion gases exiting the combustor downstream into a corresponding row of rotating turbine blades. Collectively, one row of nozzles and one row of turbine blades make up a stage.
The rows of stationary vanes and turbine blades operate at extremely high temperatures and must be cooled by airflow or other cooling medium to ensure adequate service life. The stationary vanes are often configured as an annular array of stator components having airfoils or airfoil-shaped vanes that extend radially between annular inner and outer bands which at least partially define a primary flow or hot gas path through the nozzle.
The temperatures within gas turbines may exceed 2500° F. Due to these extreme operating temperatures within the gas turbine engine, it is desirable to utilize materials with a low coefficient of thermal expansion for the airfoils and/or the inner and outer bands. For example, to operate effectively in such strenuous temperature and pressure conditions, composite materials have been suggested, in particular for example, ceramic matrix composite (CMC) materials. Not only do the CMC materials have a relatively low coefficient of thermal expansion, but also CMC materials have higher temperature capability than metallic parts, thus allowing for higher operating temperatures within the engine resulting in higher engine efficiency.
However, components formed from ceramic materials still have local thermal stresses when exposed to hot gas within the turbine engine. There remains a need to tailor the local thermal stresses of cooled or uncooled CMC components in response to such hot gas loading.